Ulcerative Colitis (UC) is a chronic inflammatory bowel disease affecting the large intestine, causing inflammation and ulcers. It is characterized by periods of active symptoms, or flare-ups, and remission. UC develops from a complex interplay of factors, including an abnormal immune response, genetics, and environmental influences. Understanding the immune system’s role in UC is essential to comprehend how the disease and its treatments impact overall immune status.
Ulcerative Colitis and Immune System Activity
Ulcerative Colitis is an immune-mediated or autoimmune inflammatory condition. In UC, the immune system mistakenly attacks healthy tissue within the large intestine, leading to chronic inflammation and ulcers. White blood cells are continually sent to the intestinal lining, producing persistent inflammation.
While the immune system in UC is overactive in the digestive tract, this localized inflammation does not inherently immunocompromise the entire body. The disease itself does not necessarily reduce the body’s global ability to fight infections. However, without proper treatment, ongoing inflammation could affect immune function over time.
Medications That Affect the Immune System
Many individuals with Ulcerative Colitis become immunocompromised not directly from the disease, but as a result of the medications used to manage their condition. These treatments are designed to modulate or suppress the immune system to reduce inflammation. Corticosteroids, such as prednisone, are potent anti-inflammatory drugs that broadly reduce immune system activity. They work by inhibiting chemicals that cause inflammation and by decreasing the activity and volume of immune cells. While effective for acute flare-ups, corticosteroids can lead to a higher risk of infections like yeast infections or urinary tract infections because they suppress the body’s natural defenses.
Immunomodulators, including medications like azathioprine and mercaptopurine, also weaken or modulate the immune system’s activity. These drugs primarily function by impacting the number or function of immune cells, such as T cells, or by interfering with their ability to build DNA, thus preventing their proliferation. Because they reduce the body’s inflammatory response, immunomodulators can increase susceptibility to various infections. It can take several months for these medications to reach their full effect, so they are often used for long-term maintenance of remission.
Biologic therapies represent a more targeted approach, blocking specific immune pathways that contribute to inflammation. For instance, TNF inhibitors (e.g., infliximab, adalimumab) neutralize tumor necrosis factor-alpha (TNF-α), a protein that promotes inflammation. Integrin inhibitors, like vedolizumab, work by preventing certain immune cells from entering the inflamed gut tissue. Additionally, IL-12/23 inhibitors, such as ustekinumab, target specific interleukins involved in the inflammatory cascade, thereby reducing inflammation. While these biologics are highly effective for moderate to severe UC, they can also increase the risk of serious infections due to their immune-modulating effects.
Living with Immune System Changes
Understanding practical implications is important for individuals whose immune systems are affected by UC medications. An increased risk of bacterial, viral, and fungal infections is common, as the immune system’s ability to fight pathogens is reduced. Recognizing signs of infection, such as fever, and reporting them promptly to a healthcare provider is important.
Vaccination is important for individuals on immune-suppressing therapies. Patients with UC should stay up-to-date with vaccinations, including annual influenza and pneumococcal vaccines. However, live vaccines, containing weakened viruses or bacteria, require careful consideration. Live vaccines (e.g., MMR, chickenpox) are typically avoided on immunosuppressive therapies due to the risk of developing the disease from the vaccine. Healthcare providers discuss vaccination schedules and recommend inactivated alternatives when available.
General precautions can help reduce exposure to infections:
- Frequent hand washing with soap and water for at least 20 seconds.
- Avoiding close contact with sick individuals and minimizing time in crowded public places, especially during peak illness seasons.
- Covering cuts and scrapes and monitoring them for signs of infection.
- Informing all healthcare providers about your UC diagnosis and current medications for coordinated care.